Vapor phase cracking apparatus



- Mafch 24, 1936. G. M. PFAU ET AL 2,035,275

VAPOR PHASE CRACKING APPARATUS Filed March 25, 1933 m r Om 11/ 28 FM a6INVENTOR. George M. Pfau, Henry .H. Pruiff. BY I I Patented Mar. 24,1936 U NI TED S TAT E. S

VAPOR PHASE CRACKING APPARATUS George M. 'Pfau and Henry Harris Pruitt,Fort Worth, Tex., assignors to Texas Pacific Coal & Oil "GoJFort Worth,-Tex., a corporation of Texas .ApplicationMarch25, 1933, Serial No.662,676

8 Claims.

This invention relates to apparatus for .the conversion of higherboiling hydrocarbons to produce hydrocarbons of a lower boiling range ofthe .order of gasoline, and more particularly relates to an improvedexpander foruse in the cracking of oils while substantially in the vaporphase.

Ina companion application of .-I. Morris Levine, filed April 25, 1933,Serial No. 667,766 a double shell type of expander is described, saidexpander having heating tubes extending therethroug-h for internalheating and a flue casing or shell around its exterior, servingas a fluefor eifectin external heating. Such an expander hasmany l5 advantagesover prior forms of expanders or heat exchanging devices for the properheating of vapors and is used with greater safety. In accordance withthe present invention we have found that certain improvements could bemade 2 on such .prior construction as will be hereinafter described.

(It'is one of the principal objects of our invention to provide anexpander or heat exchange apparatus 'for vapor phase cracking which willeffectively and uniformly raise the temperature of the vapor .to andmaintain them withinthat range .best suited for the particular crackingstock'being treated. I

Another object of our invention is to provide a heat exchange apparatusfor uniformly increasing the temperature of hydrocarbons particularly inthe vapor state, which apparatus may be easily and quickly dismantledfor the removal of carbon and other materials deposited on the internaland external surfaces.

.Another object of the invention is to provide a heat exchange andexpander chamber pierced by a ,plurality of heating tubes securedto .endplates .in which the entire bundle oftubes may lie-removed as a unit forcleaning and inspection.

Other objects andadvantages of ourinvention will .appearfrom thefollowingdescription thereof. taken -in connection with the attacheddrawing which illustrates -a preferred embodiment thereof and in whichthere is shown .a vertical sectionsubstantially through the center ofthe expander,

The rhigh temperature maintained in heat exchangers .particularly in expanders for the .cracking of higher boiling point hydrocarbons to lowerboiling point hydrocarbons is such that gaseous seals are maintainedwith difficulty. It is .essential .that the expander chamber receivingthe vapors to be cracked be leak-proof in order to insure operatingefficiency and safety from flashing. Such expanders, however must beperiodically cleaned to remove the unavoidable carbon deposits, for suchdeposits materially reduce'the heat exchange efficiency of the expander,and interfere with the uniform conduction of the heat through thevarious parts of the expander.

We have therefore developed an expander device capable of effectinguniform heating ofthe vapors introduced into the vapor chamber and 10which may be dismantled, cleaned and inspected as often as necessary. Inparticular it consists of an outer chamber enclosed by wall or shell l0which may be of brick or other suitable heat resistant .or refractorymaterial, said chamber be- 5 ing adapted to receive hot gases throughthe opening I I from any suitable source, such as'from a furnace (notshown) either combustion gases or hydrocarbon gases being suitable. Foref-, fective operation, the shell l9 preferably is ver- 20 ticallydisposed although other positions may be found suitable. Inasmuch as thecracked vapors and the heated gases naturally tendto rise, and aconstant and uniformflow of both is de- I sired, the stack shape orvertical position is most 25 satisfactory. 7 V n Mounted within the fluewall In and spaced therefrom is .a vapor chamber or expander having ashell or wall. 12, which chamber receives the vapors to be convertedthrough the inlet I3 hav- 30 ing an extension conduit l4 adapted toconvey thevapors substantially to the bottom of the chamber. The spacel5 between the expander wall 10 and the flue gas wall l2 serves as aconduit for a portion of heating gases passing u 3 wardly therethrough,which gases uniformly heat the outer wall of the vapor chamber. Theremaining gases pass through a series of tubular conduits or heatingtubes l6 which extend through the vapor chamber and which, areequidistantly spaced from each other and in a preferred constructionalso from the walls, said tubes being secured to the end plates of theshell l2 as hereinafter described.

The advantages, of this general construction are set forth more indetail in the companion application of I. Morris Levine heretoforementioned.

The tubular conduits 16 are sealed in the 'top end plate l'l and to thebottom end plate l8,by any desired method as welding, rolling orotherwise. The bottom plate 18, is in the form of a round invertedbox-like structure having an opening boundedby flanges l9 whichcooperate with inwardly projecting flanges 20 extending'inward- 1y fromthe wall l2 of the expander chamber to secure the structure in position.Suitable bolts, clamps or other securing devices 2! are employed to jointhe flanges l9 and 20 to form an efiective seal against vapor leaks. Theupper plate I! is also bolted, sealed or otherwise attached by securingmeans 22 to an outwardly turned flange 23 formed on the upper end of thewall l2 of the vapor chamber. Other methods of attachment may beemployed if desired. For example, it has been found that a tongue andgroove arrangement together with a high temperature resistant gasket isespecially effective in securing the end plates I! and IE to the flanges22 and 20 respectively.

The hydrocarbon vapors to be cracked are heated to relatively highcracking temperature in the expander by the heated gases which pass boththrough the bank of tubes l6 spaced substantially equi-distantly fromeach other and through the annular space'or channel I 5 between thetwowalls or shells.

The expander is supported in the shell 10 by means of a perforatedsupporting ring 24, formed on, welded or otherwise attached to the walll2 which in turn is supported by a perforated annular ring 25, restingupon a series of brackets 26 attached to the flue wall 10. The size andnumber of holes or slots in these rings are such that the division ofthe heating gases as between the tubes I 5 and the space l5 effectsuniform heating of the vapors within the expander chamber. By supportingthe expander only at one horizontal plane near the top, thermalexpansion and relief of stresses and strains is provided for.

The flue gas wall l0 extends some distance above the expander chamberforming a chamber 26 covered by a removable plate 21 attached by anysuitable means 28 to said wall. The vapor inlet pipe I3 as well as thevapor discharge pipe 29, connected to the top end plate I! in couplings30, pass through this plate, suitable stuffing boxes 3| being used tocompletely seal the connections. The heating gases pass from thischamber through the outlet 32.

In order to remove the tube bank for cleaning or repairing, the stuffingboxes are loosened, the inlet or outlet tubes are withdrawn and the capplate 21 is removed. The vapor chamber then may be easily lifted out ofthe flue chamber wall. By removing the bolts 2| and 22 holding the tubebank to the vapor chamber walls l2, the tube bank may be removed fromsaid walls so that the outside of each tube can be cleaned, inspected orrepaired, without separating any of the tubes from the end walls I! andI 8.

The present device can be constructed at a very low-cost and isextremely easy to dismantle. Furthermore, it is safer to operate, foreven should a leak of vapors from the inner chamber occur undercircumstances where the flue gases contain sufficient oxygen to causecombustion of the vapors, the fire will be confined to the space betweenthe chambers and likely be brought to the attention of the operatorbefore any damage is sustained. The expander is also an eflicientheat.exchanger, for the vapors are heated both internally andexternally. It is of course to be understood that either liquid phase orvapor phase hydrocarbons may be uniformly heated to cracking temperaturein the chamber.

While we have shown a preferred form of apparatus in detail, it is to beunderstood that many modifications may be made thereto without departingfrom the novel features of the present invention, and we thereforedesire a broad interpretation within the scope and-spirit of thedescription herein and of the claims appended hereinafter.

We claim:

1. An expander tank for the conversion of higher boiling pointhydrocarbons to lower boiling point hydrocarbons which consists of aninner shell forming a vapor chamber, a tube bundle mounted within saidchamber, said tube bundle being removably secured at each end to saidshell, an outer. shell forming a flue gas chamber surrounding said vaporchamber, a bafile ring within said flue gas chamber supporting saidvapor chamber, said vapor chamber and flue gas chamber havingpassageways for the passage of heating gases therethrough, one of saidpassageways comprising the tubes of said tube bundle, said tube bundleand inner shell being removable from said outer shell.

2. In apparatus for the conversion of hydrocarbon oils into lowerboiling hydrocarbon oils such as gasoline, an expander tank whichcomprises an inner shell and end plates attached thereto forming a'pressure tight chamber adapted for the passage of hydrocarbons, aplurality of tubes projecting through said chamber, and attached to saidend plates,.an outer shell surrounding said inner shell and spacedtherefrom, a conduit for introducing hot gases into said outer shell onthe exterior of said inner shell chamber, a plurality. of flue gas tubeswithin said chamber connecting said end plates, an outer shell ofrefractory material completely surrounding said inner shell, means forpassing heating gases through said outer shell and through said flue gastubes and means for introducing and removing hydrocarbon vapors intosaid conversion chamber adjacent the bottom thereof at a point near theouter periphery of the same, and means for removing said hydrocarbonvapors from said conversion chamber at a point adjacent the top thereofand diametrically opposed to the point of introduction of said Vapors.4. A heat exchange apparatus for hydrocarbons comprising an outervertical shell,.an inlet for introducing heating fluid at the bottom, anoutlet for removing the same near the top, an outer end plate removablyattached to the top of said shell, an inner vertical shell supportedwithin said outer shell and spaced therefrom having end platesremovably. attached thereto and a bank of tubes connecting the same, theshell, end plates and tubes constituting a heating chamber, inlet andoutlet conduits extending through the top end plates of said outer shelland of said inner shell, said heating chamber being removable as a unitfrom said outer shell through the top thereof upon detachment of theouter top plate attached thereto.

5. An expander tank for the conversion of higher boiling pointhydrocarbons to lower boiling point hydrocarbons comprising an outerver-' tlcal shell, means for introducing heating gases at the bottom andfor removing them near the top of said shell, an outer end plateremovably attached to the top of said shell, an inner vertical shellsupported within said outer shell and having end plates connected by aplurality of uniformly spaced heating flues forming with said shell avapor conversion chamber therebetween, inlet and outlet conduitsextending through said outer top plate and inner top plate forintroducing vapors into and for removing the same from said chamber,said inlet conduit extending to a point adjacent the bottom of saidchamber, said heating gases being adapted to pass between said shells,and means for throttling the flow of said heating gases passing betweensaid shells.

6. An expander tank for the conversion of higher boiling pointhydrocarbons to lower boiling point hydrocarbons comprising an innershell provided with end plates which, together with said shell, form avapor chamber therebetween, means for introducing hydrocarbons to beconverted into said vapor chamber, a plurality of flue gas conduitsextending through said chamber in gas tight relation thereto, saidconduits being removable as a unit from said shell, an outer shellcompletely surrounding said inner shell and spaced therefrom, and meansfor passing hot flue gases through said outer shell for passage throughsaid conduits and around said inner shell whereby they give up a portionof their heat to said hydrocarbons for conversion of the latter, saidinner shell together with its end plates and conduits being bodilyremovable from said outer shell as a unit to facilitate repair thereof.

7. In an expander tank for the conversion of higher boiling pointhydrocarbons to lower boiling point hydrocarbons, a shell having anoutwardly turned flange at one end thereof and an inwardly turned flangeat the other end thereof, an end plate removably secured to saidoutwardly turned flange, and an open ended box shaped end plate havingan inwardly turned flange secured to the inwardly turned flange of saidshell on the inner side thereof and being contained within said shell, abank of flue gas conduits extending through said shell and having theirends secured in said end plates, said box-like end plate being slidablethrough said shell for removal of the same together with said bank ofconduits from said shell, an outer shell surrounding said inner shelland in which said latter shell is suspended, means for introducingvapors to be converted into the interior of said inner shell at a pointadjacent the lower end thereof, means for conducting converted vaporsfrom the top of said inner shell, and means for passing hot flue gasesthrough said outer shell for passage through. said conduits and aroundthe outside of said inner shell.

8. An apparatus for converting hydrocarbon vapors, comprising an outervertical shell, means for introducing heating gases at the bottom andfor removing them near the top, an outer end plate removably attached tothe top of said shell, an inner vertical shell supported within saidouter shell having end plates connected by a plurality of heating flueswhich are uniformly spaced from each other throughout the entire crosssectional area of said shell and forming with said shell a vaporconversion chamber therebetween, inlet and outlet conduits extendingthrough said outer top plate and inner top plate for introducing vaporsinto and removing the same from said chamber, said inlet conduitextending to a point adjacent the bottom of said chamber.

' GEORGE M. PFAU.

HENRY HARRIS PRUITT.

